First of all re model choice the ST 2000 is heavy, a whole pound more than typical engines of that size . So something that might otherwise need weight up front to get the CG in the right place. A Fokker triplane comes to mind.

Next this will be a pretty old engine., maybe 30 years so a trial run on the bench might be a good idea just to see if it is in good order. Lots of owners did not understand how to set up the carb. RTFM! so there are lots around where different carbs have been fitted.

FUEL I may start a real argument with this but here goes. Unless your ST has been modified it is pretty certain it WILL NOT run well on standard glow fuel with 18% oil and 15% nitro, the problems will be most apparent on mid range throttle operation.. Our club had quite a few ST 2000 - 4500 owners and when we bought in our fuel in bulk we ordered Tigre Big Brute which contains 6½% E.D.L. and 4½% castor oil and was specially formulated with Mick Wilshere, who was the UK agent and ST guru, for use with Super Tigre 2000 engines and above. This was a low nitro fuel. In fact it might have been zero nitro thinking about it. I do know that they ran better on low nitro fuels say 5% max.

It will swing a big prop. 16x8 or 18x6 are good starting points.

There is a wealth of discussion on the big STs on our Glow engine forum.